BARACK OBAMA yesterday unleashed Bill Clinton as his secret weapon as he nosed ahead days before the US election.

Polls yesterday suggested the Democrat had a slim lead on Republican Mitt Romney in the most critical battlefield states.

And that was before he turned to the star quality of former president Clinton to boost his popularity.

Clinton has already spoken at around 50 Obama campaign events and raised more than £4million for his re-election.

Commentators have claimed his charisma and enduring popularity have helped keep his successor in the race after Romney mounted a far better campaign than the Democrats expected.

Last night, Obama and Clinton were preparing to address a joint rally in Virginia – a state with 13 electoral votes to be won.

President Barack Obama waves to supporters

Yesterday, pop star Katy Perry appeared with Obama at a rally in Milwaukee.

Obama had been trailing Romney after poor performances in head-to-head debates, but a poll by Reuters/Ipsos yesterday put Obama on 47 per cent and Romney on 46 per cent. The vote is on Tuesday.

In a speech in Ohio on Friday, Obama name-dropped Clinton four times. He said: “For eight years, we had a president who shared our beliefs and his name was Bill Clinton.

“His economic plan asked the wealthiest Americans to pay a little more so we could reduce our deficit and invest in the skills and ideas of our people.”

Obama said Republicans, including Romney, opposed that plan and his arithmetic “was just as bad back then as it was today”.

Obama and Clinton have had a fraught relationship since Obama beat his wife Hillary to be the Democratic candidate in the 2008.

Obama angered Clinton in 2008 when he said Ronald Reagan “changed the trajectory of America in a way that Richard Nixon did not and that Bill Clinton did not”.

And the same year, Clinton called Obama’s history of opposing the Iraq war a “fairy tale.” But with Obama struggling in the polls, they were forced to put their differences aside to stop a Republican entering the White House.

Clinton’s reputation may have been tarnished by the Monica Lewinsky scandal but he remains one of America’s most popular presidents.

His speech at the Democratic National Convention in September gave Obama a massive boost in the polls.

And Clinton has worked tirelessly for the Obama campaign since then. On Friday alone, he spoke at five events in Florida – a key swing state. In St Petersburg, Clinton said: “Nobody, nobody, nobody – not me, not anybody else – could have repaired all the damage that was done in four years.”

And at Palm Beach State College, he said: “Obama’s policies are working. I want the decider-in-chief to be the guy that took us through the storm and has better plans for the future.”

The final weekend of the campaign includes another joint event in New Hampshire.

They had planned to campaign together across three states last week but the trip was called off because of superstorm Sandy.

Obama is now the bookies’ favourite to win the 57th presidential race. Around £10million has been bet on the outcome of the election. William Hill have Obama at 1-4 to win and Romney at 3-1.

Spokesman Graham Sharpe said: “In recent days, we have also taken five-figure bets for Obama from French, Belgian and Norwegian clients, as well as British ones, so this is turning into a worldwide gamble, with plenty of financial support still coming in for Mitt Romney, as the polls predict there is little between the pair.”

Despite his initial lead in the polls, Romney has been unable to achieve the breakthroughs needed in the key swing states such as Ohio, where polls show him trailing by several percent.

No Republican has been elected president without winning Ohio.

And Obama won a huge boost on Friday when figures showed more Americans were in work.

The US economy saw a higher-than-expected 171,000 jobs created in October, which Obama’s campaign team said showed the president’s policies are working.